1. Field of Invention
The present invention relates to a heatsink device, and more particularly to an active solid heatsink device and fabricating method thereof.
2. Related Art
When an electron industry process is improved from 90 nm to 65 nm or even 45 nm, the heat generation of a developed “multi-core” integrated circuit (IC) has been reduced from 130 W (watt) to 80 W. In this manner, although the high heat generation problem has been solved, the problem of hot spots occurs on an IC chip. A so-called hot spot is a local heat-generating portion with an area of approximately 50 μm (micrometer)*50 μm. On the hot spots, a local heat flux can be up to 150 W/cm2 to 1000 W/cm2. At the same time, the generation of the hot spots will lower the performance of the IC chip (e.g. a processor). Although a conventional heatsink device (e.g. air cooled type or air cooled type used in conjunction with the heat pipes) can settle down the problem of the total heat generation of the processor, the hot spots cannot be effectively eliminated. Therefore, there is a need for a new cooling technique capable of eliminating the problem of the hot spots.
On the other hand, on the application of the light emit diodes (LEDs), the improvement of the light-emitting brightness of the LEDs will increase the heat generation amount per unit unit area of the LEDs, and thus a heat-generating density is continuously increased. At the same time, since the package structure of the LEDs is different from that of common ICs, the heat dissipation manner of the LEDs is also different of that of the common ICs. Therefore, the heat dissipation problem of the LEDs is also a technical bottleneck to be solved by the photoelectric semiconductor industry. Currently, mostly solder ball bumps or bonding pads are used as the heatsink bodies for transferring the heat to the heatsink device fin or the substrate in a heat conduction manner, so as to dissipate the heat. Although the similar passive heat dissipation methods are integrated in the package structure of the LEDs, for providing the heat dissipating capability, the heatsink bodies transfer the heat from a hotter heat source to a colder heatsink device component based on a basic law of thermodynamics, and then the heatsink components exchanges the extra heat through the heat conduction and heat convection. Thus, the heat dissipation effect is poor. Then, a solid active heatsink device is developed to provide more direct and efficient cooling capability.
A conventional active solid heatsink device is a thermo-electric (TE) element. The TE element is also called a refrigerator, which is an active cooling technique and has the effect of reducing the temperature to below the room temperature. The TE element uses a carrier of the semiconductor as a heat conduction medium, and the energy required by the electron to flow is provided by an externally applied direct current (DC). Thus, the carrier flows from a cold end to a hot end, thereby transferring the heat from one end to the other end and achieving the heat dissipation effect. In other words, when the TE element is powered, the electrons start from a negative electrode, pass through a P-type semiconductor channel and absorb the heat energy therein, then reach an N-type semiconductor channel and release the heat energy. Here, once passing through one P-N module, the heat energy is transferred from one end to the other end. In this manner, the heat energy is actively pumped to cause the temperature difference, thereby forming the cold and hot ends. The TE element can be used to control the temperature, and the structure thereof is simple. Therefore, the refrigerant is not required, and mechanical parts are omitted, thus eliminating noises.
Another active solid heatsink device is a thermionic (TI) element. An operating principle of the TI element is similar to that of the TE element. The TI element includes two spaced metal electrodes. By applying a potential difference between the two metal electrodes, the electron flow is driven to flow from one electrode to the other electrode. At the same time, as the energy is transferred, i.e. the electrode where the net electrode flow origins becomes cool, and the electrode where the net electrode flow terminates becomes hot. Due to the physical limitations, the conventional TI element cannot achieve the cooling requirements under the normal temperature. Therefore, the semiconductor material is used as the medium between the electrodes, so as to improve the net electron flow (conductivity) of the TI element. By using the heterogeneous structure semiconductor (e.g. super lattice semiconductor material) as the medium, the conductivity of the TI element can be improved, and meanwhile the heat conduction coefficient of the semiconductor can be reduced, so as to prevent the heat energy of the hot end flowing back to the cold end due to the temperature difference, thereby improving the efficiency of the TI element.
However, in the conventional active solid heatsink device, a single pin area is larger than or equal to the area of the hot spot, and the high heat-generating density of the hot spot exceeds a heat load of a single pin. Therefore, the effect of merely using the active solid heatsink device for eliminating the hot spots is quite limited.